An outbreak of Streptococcus suis serotype 2 emerged in the summer of 2005 in Sichuan Province, and sporadic infections occurred in 4 additional provinces of China. In total, 99 S. suis strains were isolated and analyzed in this study: 88 isolates from human patients and 11 from diseased pigs. We defined 98 of 99 isolates as pulse type I by using pulsed-field gel electrophoresis analysis of SmaI-digested chromosomal DNA. Furthermore, multilocus sequence typing classified 97 of 98 members of the pulse type I in the same sequence type (ST), ST-7. Isolates of ST-7 were more toxic to peripheral blood mononuclear cells than ST-1 strains. S. suis ST-7, the causative agent, was a single-locus variant of ST-1 with increased virulence. These findings strongly suggest that ST-7 is an emerging, highly virulent S. suis clone that caused the largest S. suis outbreak ever described.

We report here a facile approach for flexible integration of high efficiency surface enhanced Raman scattering (SERS) monitors in a continuous microfluidic channel. In our work, femtosecond laser direct writing was adopted for highly localizable and controllable fabrication of the SERS monitor through a multi-photon absorption (MPA) induced photoreduction of silver salt solution. The silver substrate could be shaped into designed patterns, and could be precisely located at the desired position of the microchannel bed, giving the feasibility for real-time detection during reactions. SEM and TEM images show that the silver substrates were composed of crystallized silver nanoplates with an average thickness of 50 nm. AFM results reveal that the substrates were about 600 nm in height and the surface was very rough. As representative tests for SERS detection, p-aminothiophenol (p-ATP) and flavin adenine dinucleotide (FAD) were chosen as probing molecules for microfluidic analysis at visible light (514.5 nm) excitation, exhibiting an enhancement factor of ~10(8). In addition, the combination of the SERS substrate with the microfluidic channel allows detection of inactive analytes through in situ microfluidic reactions.

We report polarized femtosecond laser-light-mediated growth and programmable assembly of photoreduced silver nanoparticles into triply hierarchical micropatterns. Formation of erected arrays of nanoplates with a thickness as small as λ/27 (λ, the writing laser wavelength) level is demonstrated. The growth mechanism of nanoplates has been clarified: (i) the excited surface plasmons enhance the local electric field and lead to spatially selective growth of silver atoms at the opposite ends of dipoles induced on early created silver seeds; (ii) the optical attractive force overcomes electrostatic repulsion in the enhanced local electric field to assemble the silver nanoparticles directly. The triply hierarchical micropattern shape and location, the nanoplate orientation, and thickness are all attained in controlled fashion.

We report fabrication of silica convex microlens arrays with controlled shape, size, and curvature by femtosecond laser direct writing. A backside etching in dye solution was utilized for laser machining high-fidelity control of material removal and real-time surface cleaning from ablation debris. Thermal annealing was applied to reduce surface roughness to 3 nm (rms). The good optical performance of the arrays was confirmed by focusing and imaging tests. Complex 3D micro-optical elements over a footprint of 100 × 100 µ m 2 were ablated within 1 h (required for practical applications). A material removal speed of 120 µ m 3 / s ( 6 × 10 5 n m 3 / p u l s e ) was used, which is more than an order of magnitude higher compared to backside etching using a mask projection method. The method is applicable for fabrication of micro-optical components on transparent hard materials.

Silver (Ag) seeds for assisting femtosecond laser direct writing (FsLDW) were employed in the fabrication of microelectrodes (MEs). Pattern-controllable and size-tunable MEs can be easily constructed by introducing Ag seeds to the ion precursor solution in the process of laser-induced photoreduction of the Ag ions. The fabrication process is stable under sufficient material supply, and the applied laser power is reduced to one-tenth of that without Ag seeds. Finally, as a representative application, an organic field effect transistor (OFET) was fabricated, based on this laser-fabricated Ag ME. The OFET exhibited good photoelectric properties, and achieved an on-off ratio of 200.

Femtosecond laser-induced periodic subwavelength and deep-subwavelength structures (SWS; DSWS) have attracted attention due to their subdiffraction resolution of surface and inner volume patterning. Understanding of the richness of laser-matter interaction during formation of SWS and DSWS is another quest which can help to find control for nanoscale fabrication. Lack of control over SWS and DSWS formation has impacted their wider use and calls for a deeper insight into the relationship between them. Herein we present a systematic study defining a criterion for imprinting either SWS or DSWS, which is based on a competition and their mutual incompatibility discriminated by the laser fluence and pulse accumulation. Structure evolution of SWS and DSWS is highly dependent on the localized effective laser fluence, which determines the instantaneous optical permittivity by the laser-excited electrons creating an active plasma layer. The proposed universal SWS and DSWS competition mechanism involving the laser-induced plasma wave at the plasma-substrate interface ties together many previous observations and unifies the discussed mechanisms of surface nanoripple formation.

This work developed a method of femtosecond laser (fs-laser) parallel processing assisted by wet etching to fabricate 3D micro-optical components. A 2D fs-laser spot array with designed spatial distribution was generated by a spatial light modulator. A single-pulse exposure of the entire array was used for parallel processing. By subsequent wet etching, a close-packed hexagonal arrangement, 3D concave microlens array on a curved surface with a radius of approximately 120 μm was fabricated, each unit lens of which has designable spatial distribution. Characterization of imaging was carried out by a microscope and showed a unique imaging property in multi-planes. This method provides a parallel and efficient technique to fabricate 3D micro-optical devices for applications in optofluidics, optical communication, and integrated optics.

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